• 2.4 baseline — 0.6 × season 2.4 (9 gm) + 0.4 × last 10 2.4
• −0.1 opponent leak — they concede 53.8/game vs a 56.6 league average
• +0.3 at this ground — averages 2.8 there (12 gm)
• vs them: averages 2.4 over 8 games — evidence, never summed

Derived, not measured — plain arithmetic over his real games, shown in full. Adjustments can overlap (a game at this ground can also be a wet one); they add simply, and this note is the admission.